Power piston with control valve



O. H. BANKER POWER PISTON WITH CONTROL VALVE Nov. 4, 1958 8 Filed Nov.19, 1956 United tates Patent Ofihce 2,858,804 Patented Nov. 4 1958 POWERPISTON WITH CONTROL VALVE Oscar H. Banker, Evanston, Ill., assiguor toNew Products Corporation, Skokie, Ill., a corporation of DelawareApplication November 19, 1956, Serial No. 623,102

8 Claims. (Cl. 121-45) The improved hydraulic control mechanismcomprising the present invention has been designed for use primarily inconnection with metal working machines for feeding a cutting or abradingtool to the work or vice versa in such a manner that the movement of thetool against the work will be varied substantially in inverse proportionto the resistance encountered by the tool. The invention is, however,capable of other uses and may, if desired, with suitable modification ifnecessary, be employed in the manner of a power'transmission orservo-mechanism for effecting application of increments of power to amovable member to shift its position in substantially inverse proportionto the resistance offered against such movement.

It is an object of this invention to provide a hydraulic piston andcylinder assembly wherein the rate of admission of fluid under pressureto the cylinder for pistondriving purposes is a function of themechanical resistance encountered by the piston against longitudinaldisplacement thereof within the cylinder.

A similar and related object of the invention, in a power cylinderassembly of this character, is to provide such an arrangement whereinthe variable porting necessary to effect such variable admission offluid under pressure into the cylinder for piston-driving purposes iswholly contained in and carried by the piston assembly itself and isoperated solely under the control of the mechanical resistance offeredto the pistonagainst displacement thereof, thereby eliminating thenecessity for employing external pressure sensing devices such aspressure-sensitive switches and the usual solenoid actuated valvescontrolled thereby. Stated more generally, it is an object of theinvention to provide a power cylinder assembly of the character brieflyoutlined above which is entirely hydraulic in its operation and iscompletely devoid of electrically operating instrumentalities.

Other objects and advantages of the invention, not at this timeenumerated, will become more readily apparent as the followingdescription ensues.

In the accompanying single sheet of drawings forming a part of thisspecification a preferred embodiment of the invention has been shown. inthese drawings:

Fig. l is a fragmentary sectional view taken substantially centrally andlongitudinally through a power cylinder assembly constructed inaccordance with the principles of the present invention;

Figs. 2 and 3 are fragmentary sectional views similar to Fig. 1 showingthe operative parts of the assembly in different positionalrelationships; and

Fig. 4 is a cross-sectional view taken substantially along the line 4-4of Fig. 1.

Referring now to the drawings in detail, a fragment of the powercylinder assembly of the present invention is shown at and comprises acylinder 12 within which there is slidably disposed a piston assembly 14mounted on the free end of a piston rod 16. The hydraulic motive fluid iapplied to the system, as schematically shown in Fig. I, through aflexible intake and return line 18 under relatively high pressure from acontrol valve 20 operatively connected to a source of fluid or reservoir22 through a feed line 24 and a pump 26. A return line 28 serves toconduct ex= haust fluid back to reservoir 22. One end of cylinder 12 isshown closed by a cylinder head 30 which may be threadedly received asat 32 on the cylinder and which, in combination with the piston assembly14', provides'a variable volume pressure chamber 34.

The piston rod 16 constitutes a thrust member operatively connected to acutting tool or other work engaging member (not shown). Alternatively,the rod 16 may be operatively connected to the work undergoing cuttingand the movements of the rod thus imparted to the work to force the sameagainst the "tool. Rod 16 is formed with a longitudinally extendingcentral bore 36 therein in communication with the line 18 at or adjacentone end of the rod and, at the othe'r end of the rod, the bore is closedby a threaded plug 38 having an Allen wrench socket 40 formed therein.The right hand end of the piston rod 16, as viewed in Figs. 1 to 3inclusive, is reduced to provide a cylindrical surface 42 on which isslidably mounted the piston as sembly 14.

The piston assembly 14 includes a cylindrical piston 44 having a centralbore 46 therein closely fitting around the cylindrical surface 42 on thepiston rod 16 but slidable thereon as aforesaid and sealed thereto byone or more O-rings 48 disposed in circumferential grooves preferablyformed in the reduced portion of the rod 16. The piston 44 is alsoslidable within bore 50 of cylinder 12 and may be sealed thereto byexpansible sealing rings 52 in the form of V-rings or the like.

Piston 44 is movable on the cylindrical surface 42 of the piston rod 16between an extreme retracted posh tion in which it abuts against a snapring '5 received within a circumferential groove 56 formed near the endof rod 16, and an advanced position wherein the opposite side thereofabuts against a thrust washer or plate 58 which surrounds the reducedend of the rod 16 and, in turn, abuts against a shoulder 60 formed onthe latter.

As best seen in Fig. 4, the rear face of the piston 44 is formed with aseries of circumferentially spaced sockets, alternate sockets beingdesignated at 62 and 64, respectively. While any number of such sockets62 and 64 may be provided in piston 44, t.ree of the sockets 62 andthree of the sockets 64 have been illustrated here? in. Disposed in eachsocket 62 and compressed between thrust plate 58 and piston 44 is aspring 66, the three such springs normally serving to yieldingly urgepiston 44 to the right as viewed in Fig. 1 against the snap ring 54 toits fully retracted position. Compressed in each socket 64 is a spring68, one e d of which bears against the bottom of the socket and theother end of which bears against a radial flange 76 formed on a plunger72 having a nose portion or button 74 formed thereon which projectsoutwardly of the socket 64. A snap ring 76 serves to retain each plunger2 in position within its respective socket 64. When piston 44 is in itsfully retracted position as shown in Fig. i, the outer end of the noseportion 74 of each plunger '72 is maintained slightly spaced from therear face of thrust plate 58 for a purpose that will be made clearpresently.

The bore 36 formed centrally in the piston rod 16 communicates throughone or more radial passages 80 with an annular groove 82 formed in thecylindrical surface 42 of the rod 16 near the forward free end there of.The bore 46 of piston 44 is formed with an internal groove 84 which maybe of slightly greater width than the width of the groove 82 and whichnormally fully registers with the latter groove when piston 44 is infully retracted position. Groove 84 communicates with chamber 34 throughan inclined passage 86.

In the operation of the herein described hydraulic control mechanism, aconstant and relatively high head of pressure is maintained within thebore 36 by valve 20 so that when the cutting tool is idling, as forexample, prior to the time the work is engaged thereby, a maximum volumeof fluid will be delivered to chamber 34 (Fig. 1) through the bore 36,radial passages 80, grooves 86 and 84, respectively, which, at thistime, are in full register, and inclined passages 86. Since little or noresistance is offered to the movement of the piston rod 16 to the leftas viewed in Fig. 1 rapid entry of fluid under pressure into chamber 34will force the entire piston assembly and piston rod 16 to the left asviewed in Fig. 1 without compressing the spring 66 or otherwise alteringthe relative positions of the various parts of the assembly as depictedin Fig. l and such movement will continue until the tool engages thework. In this manner all initial lost motion between the operating orcutting tool and the work will be rapidly and completely taken up.

As soon as the cutting tool strikes the work to make its initial cut, aresistance to further advance movement of the piston rod 16 will bebuilt up, and the rod will be held against its free floating advancemovement so that an increase in pressure within the chamber 34 will takeplace. Such an increase in pressure within chamber 34 will cause piston14 to move to the left as viewed in Fig. l relative to rod 16 againstthe action of springs 66 until such time as the extreme forward ends ofthe nose portions or buttons 74 of the plungers 72 engage the thrustplate 58. During such relative movement between piston 44 and reducedcylindrical portion 42 of the rod 16, the grooves 82 and 84 will move toa position of partial register as shown in Fig. 2 to reduce the rate offlow of fluid into chamber 34 through the previously described pathprovided for it. Grooves 82 and 84 thus, in effect, provide arestriction in the normal path of flow of the motive fluid so that therate of expansion of the volume of the pressure chamber 34 is reduced toan extent which is commensurate with the cutting rate of the tool on theparticular work involved. Thereafter the pressure of the plungers 72acting on the thrust plate 58 under the influence of the springs 68 andof the advancing piston body 44 will serve to continue the advancingmotion of the piston rod 16 at the desired rate.

It will be understood, of course, that the design of the various fluidpassages and of the springs 68 will be calculated according toengineering exigencies so that for any given tool and any given work thedesired rate of advancement of the tool will be effected. It will beobserved that under normal operating conditions slight increases orslight decreases in the resistance of the work to the advance movementsof the tool will be absorbed by the combined resistance of thecompressed or preloaded springs 68 without materially compressing themfurther. Thus a slight increase in this resistance will cause theplungers 72 to increase their pressure against the thrust plate 58 toadvance the piston rod 16 and consequently the tool. Conversely, aslight decrease in this resistance will cause the plungers 72 todecrease their pressure upon the thrust plate 58.

When an unexpected obstruction is encountered, as for example, a hardspot in the work, or a change in the cutting angle of the tool, theinability of the piston rod 16 to continue to advance will cause theplungers 72 to be retracted into their respective sockets 64 against theresistance of springs 68 to such an extent that the grooves 82 and 84move out of register (Fig. 3), thus shutting off the supply of fluidunder pressure to chamber 34 and terminating the tool feed, but holdingthe tool against the work with the locked-in pressure in chamber 34.This steady pressure will obtain until the resistance is overcome androd 16 may move forward again relative to piston 44 to cause grooves 82and 84 to come into at least partial registry. This allows fluid toenter chamber 34 again and resume movement of piston 44 to the left.

In instances where successive cuts are to be made progressively on aparticular work, as the tool breaks through or otherwise completes eachsuccessive entire cut, resistance to advancement of the tool willsubstantially cease and springs 68 and subsequently springs 66 willexpand so that piston 44 is slid on rod 16 to its fully retractedposition on the rod 16 and thus the ports or grooves 82 and 84 are movedinto full register and cause unobstructed flow of fluid into thepressure chamber 34 rapidly to advance the piston rod 16, andconsequently the tool, to its succeeding work-engaging position.

The foregoing description is illustrative of a preferred form of theinvention, but it should be understood that the scope of the inventionis not to be limited thereto, but is to be determined by the appendedclaims.

I claim:

1. In a hydraulic control mechanism of the character described, incombination, a cylinder member closed at one end, a piston .rod memberprojecting into said cylinder member in axial alignment therewith, saidmembers being axially movable relative to each other, one of saidmembers being designed for operative connection to a cutting tool or thelike whereby movement of the member in one direction relative to theother member will cause the tool to be advanced proportionately, apiston body slidable on said piston rod toward and away from said closedend, said piston body also being slidable within the cylinder and, incombination with the closed end of the latter, providing a variablevolume fluid pressure chamber, a source of fluid under pressure, saidpiston rod having a longitudinal passage therein communicating with aradial port at the piston body and said piston having a passage leadingfrom the chamber to a radially disposed port at the piston rod, manuallycontrolled means for directing fluid under pressure from said source tosaid longitudinal passage in the piston rod, said ports on the pistonbody and piston rod varying in registry with one another from fullregistry when the piston body is in its fully retracted position to zeroregistry when the piston body is in its advanced position to control theadmission of fluid under pressure to said chamber, means for exhaustingthe fluid under pressure from said chamber through said piston rod andpiston body passages, and spring means interposed between said pistonbody and piston rod for yieldingly maintaining said piston body in itsfully retracted position on the piston rod.

2. In an hydraulic control mechanism of the character described, incombination, a cylinder member closed at one end, a piston rod memberprojecting into said cylinder member in axial alignment therewith, saidmembers being axially movable relative to each other, one of saidmembers being designed for operative connection to a cutting tool or thelike whereby movement of the member in one direction relative to theother member will cause the tool to be advanced proportionately, apiston body slidable on said piston rod between advanced and retractedpositions thereon, said piston body also being slidable within thecylinder and, in combination with the closed end of the latter,providing a variable volume fluid pressure chamber, said piston rod andpiston body being provided with cooperating ports which are in fullregister with each other when the piston body is in its retractedposition and which are out of register when the piston body is in itsadvanced position, said piston rod and piston body functioning as avalve for admission of motive fluid to said chamber by virtue of varyingdegrees of registry between said ports, means on said piston rodestablishing a rearwardly facing surface, means on said piston bodyestablishing a forwardly facing surface, a coil spring interposedbetween said surfaces yieldingly maintaining said piston body in itsfully retracted position, and additional spring means interposed betweensaid piston body and piston rod and effective when the former is in anintermediate position on the latter for transmitting further forwardmovements of the piston body to the piston rod.

3. In an hydraulic control mechanism of the character described, incombination, a cylinder closed at one end, a piston rod projecting intosaid cylinder in axial alignment therewith and adapted to be operativelyconnected to a cutting tool or the like whereby movement of the pistonrod forwardly in one direction will elfect advance movements of thetool, a piston slidable on said piston rod between advanced andretracted positions thereon, said piston also being slidable in thecylinder and, in combination with the closed end of the latter,providing a variable volume fluid pressure chamber, said piston rod andpiston being provided with cooperating ports which are in full registerwith each other when the piston is in its retracted position and whichare out of register when the piston is in its advanced position, saidpiston and rod functioning as a valve for admission of motive fluid tosaid chamber by virtue of varying degrees of registry between saidports, spring means interposed between said piston and piston rod foryieldingly maintaining said piston in its fully retracted position, andadditional spring means interposed between the piston and piston rod andeffective when the former is in an intermediate position on the latterfor transmitting further movements of the piston toward its advancedposition directly to the piston rod.

4. In an hydraulic control mechanism of the character described, incombination, a cylinder closed at one end, a piston rod projecting intosaid cylinder and adapted to be connected operatively to a cutting toolor the like whereby movement of the piston rod forwardly in the cylinderwill effect advance movements of the tool, a piston slidable on saidpiston rod between advanced and retracted positions thereon, said pistonalso being slidable in the cylinder and, in combination with the closedend of the latter, providing a variable volume pressure chamber, saidpiston and rod being provided with cooperating ports which are in fullregister with each other when the piston is in its retracted position,said piston and rod functioning as a valve for admission of motive fluidto said chamber by virtue of varying degrees of registry between saidports, means providing an annular rearwardly facing surface on saidpiston rod, a plurality of longitudinally extending, circumferentiallyspaced springs interposed between said rearwardly facing annular surfaceand said piston for yieldingly maintaining said piston in its fullyretracted position, and a second set of longitudinally extendingcircumferentially spaced springs interposed between said rearwardlyfacing annular surface and said piston and effective when the former isin an intermediate position on the piston rod for transmitting furtherforward movements of the piston to the piston rod.

5. In an hydraulic control mechanism of the character described, thecombination set forth in claim 4 wherein said second set of springs aremounted on and wholly supported by said piston.

6. In an hydraulic control mechanism of the character described, incombination, a cylinder closed at one end, a piston rod projecting intosaid cylinder and adapted to be operatively connected to a cutting toolwhereby movement of the piston rod forwardly in the cylinder will effectadvance movements of the tool, a piston slidable on said rod adjacentthe rear end thereof between advanced and retracted positions thereon,said piston also being slidable in the cylinder and, in combination withthe closed end thereof, providipg a variable volume fluid pressurechamber, there being a longitudinally extending bore in said piston rod,said piston rod being formed with an external annular groove adjacentthe rear end thereof and with a radial passage establishingcommunication between said bore and groove, said piston being formedwith an internal annular groove in communication with said externalgroove in the piston rod when the piston is in its fully retractedposition, said internal groove being out of communication with saidexternal groove when the piston is in its advanced position, said pistonalso being formed with a passage establishing communication between saidinternal groove and the pressure chamber, spring means interposedbetween said piston and piston rod normally urging the former to itsretracted position on the latter, and second spring means interposedbetween said piston and piston rod and effective when the former is in apredetermined intermediate position on the piston rod for yieldinglytransmitting further forward movements of the piston to the piston rod.

7. In an hydraulic control mechanism of the character described, incombination, a cylinder closed at one end, a piston rod projecting intosaid cylinder and having a reduced rear end providing a cylindricalsurface, said piston rod being adapted to be operatively connected to acutting tool whereby the movements of the rod in a forward directionwill effect advance movements of the tool, a piston slidable on andsealed to said cylindrical surface and, in combination with said closedend, providing a pressure chamber, a radial shoulder formed on saidpiston at the forward end of said cylindrical surface, means providingan abutment on said piston rod adjacent the rear end thereof, saidpiston being movable between a retracted position wherein it effectivelybears against said abutment to an advanced position wherein iteffectively bears against said shoulder, a plurality ofcircumferentially spaced coil springs each effectively hearing at oneend against said shoulder and at the other end against said piston andserving to yieldingly urge said piston toward its retracted position,said piston and piston rod being provided with cooperating ports whichare in full register with each other when the piston is in its retractedposition and which are out of register when the piston is in itsadvanced position, said piston and rod functioning as a valve foradmission of motive fluid to said pressure chamber by virtue of varyingdegrees of registry between said ports, and a second set ofcircumferentially spaced springs interposed between said piston andshoulder and efiective when the former is in a predeterminedintermediate position to yieldingly transmit further forward movementsof the piston to the piston rod.

8. In an hydraulic control mechanism of the character described, thecombination set forth in claim 7 including a second set ofcircumferentially spaced springs interposed between said piston andshoulder and effective when the former is in a predeterminedintermediate position to yieldingly transmit further forward movementsof the piston to the piston rod.

References Cited in the file of this patent UNITED STATES PATENTS

